Reference: (D9T) Operation and Maintenance Manual, SEBU8736, "Backup Alarm - Test"
The ECM applies power to the backup alarm whenever the ECM receives a signal from the reverse direction switch.
- The backup alarm has failed.
- The harness circuit is shorted to ground. (alarm is always ON)
- The harness circuit is open. (alarm does not sound)
- The ECM has failed.
Note: Ensure that there are no active diagnostic codes for the direction switch.
Check the backup alarm.
- Disconnect the backup alarm from the harness.
- Use jumpers to connect the respective terminals of the backup alarm to a + battery and ground.
Expected Result:
The backup alarm sounds when power is applied.
Result:
YES: The backup alarm sounds when power is applied. Proceed to "The Harness Circuit Is Shorted To Ground. (Alarm Is Always On)".
NO: The backup alarm does NOT sound. The backup alarm has failed.
Repair: Replace the backup alarm.
STOP.
The Harness Circuit Is Shorted To Ground. (Alarm Is Always On)
CHECK FOR A SHORTED HARNESS
The backup alarm remains disconnected.
- Turn the disconnect switch to the OFF position.
- Disconnect the ECM from the harness.
- At the harness connector for the ECM, measure the resistance between contact J2-6 (wire 321-BR(Brown)) and all possible sources of ground.
Expected Result:
Each resistance is greater than 5000 ohms.
Result:
YES: The resistance is greater than five Ohms (no continuity). The resistance of the harness circuit is correct. Proceed to "The Harness Circuit Is Open. (Alarm Does Not Sound)".
NO:The resistance is less than five Ohms (continuity). The harness has failed. Wire (321-BR(Brown)) is shorted to ground in the harness.
Repair: Repair the harness or replace the harness.
STOP.
The Harness Circuit Is Open. (Alarm Does Not Sound)
CHECK FOR AN OPEN IN THE HARNESS
The backup alarm and the ECM remain disconnected from the harness.
- The disconnect switch remains OFF.
- At the harness connector for the ECM, place a jumper from contact J2-6 (wire 321-BR(Brown)) to ground.
- At the harness for the backup alarm, measure the resistance from wire 321-BR(Brown) to ground.
Expected Result:
The resistance is greater than 5000 Ohms.
Result:
YES: The resistance is greater than 5000 Ohms. The harness circuit has failed. Wire (321-BR(Brown)) is open in the harness between the ECM and the backup alarm relay.
Repair: Repair the harness or replace the harness.
STOP.
If the cause is not found, the Implement ECM may have failed. Refer to Troubleshooting, "Electronic Control Module (ECM) - Replace" in this manual.
NO: The resistance is less than five Ohms. The harness circuit is correct. There may be an intermittent problem.
Repair: Check the harness circuit again. With Caterpillar Electronic Technician (Cat ET), if available, perform a "Wiggle Test" on the machine wiring harness. The wiggle test may detect momentary or intermittent shorts or opens in the machine wiring harness.
If all possible causes of the problem have been investigated and no problem can be found, you may need to replace the Implement ECM.
Prior to replacing an ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time and expense. If the ECM must be replaced, refer to Troubleshooting, "Electronic Control Module (ECM) - Replace" in this manual.
STOP.